Generally, as an exterior molding body of automobile, there us used a metallic exterior panel attached on a metallic structural part. However, recently, in order to improve a mileage and running performance of automobile, there has been a demand to lighten various automobile parts and therefore there has been used a resin for the exterior panel and support structure therefor.
For example, in Patent Document 1, in order to lighten the panel for automobile, there has been a proposal of a panel for automobile comprising a fiber reinforced plastic (FRP) whose reinforced fiber is a base fabric comprising continuous fiber. However, this is not satisfactory for designability and production efficiency.
Further, in Patent Document 2, there has been a proposal of a tailgate comprising an outer panel comprising a polyphenylene ether/polyamide alloy and an inner panel comprising a long fiber reinforced polyamide/polyolefin alloy in view of lightening and modulation thereof. However, this proposal has a problem of not good setting and waving appearance by dimension change of polyamide (PA) by water absorption. In order to solve the problem of the dimension change by water absorption, there has been a proposal of using a polycarbonate/polybutylene terephthalate alloy. However, an adhesion constitution is required because the inner panel comprises a long fiber reinforced polypropylene. Further, the outer panel is affected by an anisotropy of linear expansion by the fiber orientation in the inner panel. However, there is no description for the magnification and anisotropy of linear expansion.
In Patent Document 3, there has been proposed a carbon fiber reinforced polyamide for exterior parts of vehicles having an average value of 6×10−5K−1 between a linear expansion coefficient in the flow direction and a linear expansion coefficient in the right angle direction to the flow direction at the injection molding. However, there is no description of anisotropic. In case of having large anisotropic, the degree of dimension change by change of temperature is different in the any directions. Therefore, the appearance quality is affected thereby and there is a possibility that breakage and cracking of molding parts occur by the presence of stress concentration parts, accordingly it is not preferable.
Further, in Patent Document 4, there is a description that in a thermoplastic resin molding body obtained by injection molding a fiber reinforced thermoplastic resin containing 3 to 70% by weight of a fibrous reinforcing material and having such a property that (volume)/(surface area)<2 mm, the relationship of linear expansion coefficients in the flow direction (MD) of melt resin containing fibrous reinforcing material and in the right angle direction (TD) to the flow direction at 23 to 100° C. is 0.6<(coefficient in the TD direction)/(coefficient in the MD direction)<2.5. Surely, it is required in the exterior structure for automobile to reduce the anisotropic. However, if the absolute value of linear expansion coefficient is still large, there is a possibility of deterioration of setting performance, not good effect for the around parts and deterioration of appearance quality such as not good painting and cracking of paint by linear expansion. Further, in case where in the molding, there is a part having a small cross section area molded at the narrow flow path, the fiber orientation is remarkable and the anisotropy thereof is remarkable, whereby there is a possibility of any not good effect for the entirely molding product case by case of the length of narrow flow path. However, in the document, there is no description for the shape of molding body.
Patent Document 1: Japanese Patent Application Laid-Open (KOKAI) No. 2002-127944
Patent Document 2: Japanese Patent Application Laid-Open (KOKAI) No. 2003-118379
Patent Document 3: Japanese Patent Application Laid-Open (KOKAI) No. 2002-226703
Patent Document 4: Japanese Patent Application Laid-Open (KOKAI) No. 9-296053